Modern elevators involve a lot of devices that are capable of processing information. Such devices may relate all aspects of using an elevator. For example, in all modern elevators control keys and information displays in the elevator are computer controlled. In addition to the controlling related devices there may be additional devices for informative or recreational purposes. For example, there may be information screens having changing content, such as advertisements. In addition to the information mentioned above modern elevators involve processing and transmitting safety related information. Typically elevators include a wide range of safety devices that are monitoring different objects. For example, there are safety devices that monitor if the doors of the elevator car and/or doors at the floor are not opening or closing appropriately. When such a defect is detected an alarm or information message must be transmitted to the maintenance staff. In some cases the operation of the elevator may be prevented.
As it is understood from the above, the information sent from the elevator car can be classified into classes according to the importance. Typically there is a division between safety critical information and other information. The safety critical information is of top priority and must be submitted reliably to the destination without any delays.
A conventional solution for providing the reliable and fast transmission of safety critical information is to have separate dedicated communication arrangements for safety critical information. For example, the information that is not safety critical may be transmitted using a commonly known bus systems used in building automation, such as LON (local operating network) or CAN (Controller area network). Then, for safety critical system separate arrangements have been introduced.